Dockerfile: fix build for specific arch

Dockerfile

@@ -2,8 +2,20 @@
 # nodejs 20 hangs on build with armv6/armv7
 FROM docker.io/library/node:18-alpine AS build_node_modules
 
+# Set the platform to build image for
+ARG TARGETPLATFORM
+ENV TARGETPLATFORM=${TARGETPLATFORM:-linux/amd64}
+
+# Install additional tools needed if on arm64 / armv7 / armv6
+RUN \
+  case "${TARGETPLATFORM}" in \
+  'linux/arm64') apk add --no-cache python3 make g++ ;; \
+  'linux/arm/v7') apk add --no-cache python3 make g++ ;; \
+  'linux/arm/v6') apk add --no-cache python3 make g++ ;; \
+  esac
+
 # Update npm to latest
-RUN npm install -g npm@latest node-gyp
+RUN npm install -g npm@latest
 
 # Copy Web UI
 COPY src /app